Question

 Which of the following statement is correct? [NEET 2021]
(a) Fusion of two cells is called karyogamy
(b) Fusion of protoplasm between two motile or non-motile gametes is called plasmogamy
(c) Organisms that depend on living plants are called saprophytes
(d) Some of the organisms can fix atmospheric nitrogen in specialised cells called sheath cells

Answer/Explanation

Ans. (b)
Statement in option (b) is correct.
Plasmogamy, the fusion of two protoplasts (the contents of the two cells), brings together two compatible haploid nuclei. At this point, two parent cells are present in the same cell, but the nuclei have not yet fused.
Incorrect statements can be corrected as Organisms that can fix atmospheric nitrogen in specialised cells are called heterocyst.
Karyogamy is nothing but the fusion of two nuclei means production of diploid cell $(2 n$ condition).

Question

 The size of Pleuropneumonia Like Organism (PPLO) is [NEET (Oct.) 2020]
(a) $0.02 \mu \mathrm{m}$
(b) 1-2 $\mu \mathrm{m}$
(c) $10-20 \mu \mathrm{m}$
(d) $0.1 \mu \mathrm{m}$

Answer/Explanation

Ans. (d)

Question

 Which of the following is incorrect about cyanobacteria? [NEET (Oct.) 2020]
(a) They are photoautotrophs
(b) They lack heterocysts
(c) They often form blooms in polluted water bodies
(d) They have chlorophyll- $a$ similar to green plants

Answer/Explanation

Ans. (b)
Cyanobacteria or blue-green algae are photosynthetic organisms which

Question

 Oxygen is not produced during photosynthesis by [NEET 2018]

(a) Cycas

(b) Nostoc

(c) Green sulphur bacteria

(d) Chara

Answer/Explanation

Ans. (c)

Green sulphur bacteria are anaerobic bacteria. They do not evolve oxygen during photosynthesis. Such type of photosynthesis is known as anoxygenic photosynthesis.

They do not use water as a source of reducing power. Instead, hydrogen is obtained from hydrogen sulphide.
Concept Enhancer Green sulphur bacteria, e.g. Chlorobium limicola, possesses bacteriophaeophytin as photosynthetic pigment.

Question

 Which of the following organisms are known as chief producers in the oceans? [NEET 2018]

(a) Cyanobacteria

(b) Diatoms

(c) Dinoflagellates

(d) Euglenoids

Answer/Explanation

Ans. (b)
Diatoms are chief producers in the oceans and they contribute $40 \%$ of marine primary productivity. They constitute a major group of unicellular eukaryotic microalgae and are among the most common types of phytoplanktons.

Question

Which of the following are found in extreme saline conditions? [NEET 2017]

(a) Archaebacteria

(b) Eubacteria

(c) Cyanobacteria

(d) Mycobacteria

Answer/Explanation

Ans. (a)

Archaebacteria are the most primitive form of bacteria. These live in diverse habitat, e.g. extreme hot temperature, saline condition, variable $\mathrm{pH}$, etc. Saline bacteria are called Halophiles (e.g. Halobacterium, Halococcus).

Question

 Which among the following are the smallest living cells, known without a definite cell wall, pathogenic to plants as well as animals and can survive without oxygen? [NEET 2017]

(a) Bacillus

(b) Pseudomonas

(c) Mycoplasma

(d) Nostoc

Answer/Explanation

Ans. (c)

Mycoplasma is triple layered smallest living cells. It does not have definite cell wall. It is an anaerobic organism. It cause diseases in plants (little leaf of brinjal) as well as in animals (pleuromorphic pneumonia in man).

Question

 The primitive prokaryotes responsible for the production of biogas from the dung of ruminant animals, include the  [NEET 2016 Phase I]

(a) thermoacidophiles

(b) methanogens

(c) eubacteria

(d) halophiles

Answer/Explanation

Ans. (b)

 

Question

 Which one of the following statements is wrong? [NEET 2016 Phase I]

(a) Golden algae are also called desmids

(b) Eubacteria are also called false bacteria

(c) Phycomycetes are also called algal fungi

(d) Cyanobacteria are also called blue-green algae

Answer/Explanation

Ans. (b)

 

Question

Methanogens belong to [NEET 2016 Phase II]

(a) eubacteria

(b) archaebacteria

(c) dinoflagellates

(d) slime moulds

Answer/Explanation

Ans. (b)

Methanogens belong to archaebacteria.
It contains three major classes of primitive bacteria, i.e. methanogens, halophilic and thermoacidophilic.
Methanogens are strict anaerobes, present in the gut of several ruminant. animals (e.g. cows, etc.) and are responsible for production of methane gas from the dung of these animals.

Question

 Chromatophores take part in [CBSE AIPMT 2015]

(a) photosynthesis

(b) growth

(c) movement

(d) respiration

Answer/Explanation

Ans. (a)

Chromatophores are found in members of phototrophic bacteria. They contain bacteriochlorophyll pigments and carotenoids and take part in photosynthesis. In purple bacteria, such as Rhodospirillum rubrum, the light-harvesting proteins are intrinsic to the chromatophore membranes.

Question

 Archaebacteria differ from eubacteria in [CBSE AIPMT 2014]
(a) cell membrane structure
(b) mode of nutrition
(c) cell shape
(d) mode of reproduction

Answer/Explanation

Ans. (a)
Archaebacteria different from eubacteria in that eubacteria have cell membrane composed mainly of glycerol-ester lipids, while archaebacteria have membrane made up of glycerol-ether lipid.

Question

Pigment-containing membranous extensions in some cyanobacteria are [CBSE AIPMT 2012]

(a) heterocysts

(b) basal bodies

(c) pneumatophores

(d) chromatophores

Answer/Explanation

Ans. (d)

 

Question

Which of the following are likely to be present in deep sea water? [CBSE AIPMT 2012]

(a) Archaebacteria

(b) Eubacteria

(c) Blue-green algae

(d) Saprophytic fungi

Answer/Explanation

Ans. (a)

 

Question

 The cyanobacteria are also referred to as [CBSE AIPMT 2012]

(a) protists

(b) golden algae

(c) slime moulds

(d)blue-green algae

Answer/Explanation

Ans. (d)

Question

Nuclear membrane is absent in [CBSE AIPMT 2012]

(a) Penicillium

(b) Agaricus

(c) Volvox

(d) Nostoc

Answer/Explanation

Ans. (d)
Nostoc is a prokaryote. Prokaryotic cells lack membrane bound organelles and well organised nucleus, i.e. nuclear envelope is absent.

Question

 In eubacteria, a cellular component that resembles eukaryotic cells is [CBSE AIPMT 2011]

(a) nucleus

(b) ribosomes

(c) cell wall

(d) plasma membrane

Answer/Explanation

Ans. (d)

The plasma membrane of eubacteria resembles to that of eukaryotic cell. It is made of phospholipid, protein and some amount of polysaccharides.

Question

 Organisms called methanogens are most abundant in a [CBSE AIPMT 2011]

(a) cattle yard

(b) polluted stream

(c) hot spring

(d) sulphur rock

Answer/Explanation

Ans. (a)

 

Question

 A prokaryotic autotrophic nitrogen fixing symbiont is found in [CBSE AIPMT 2011]

(a) Cycas

(b) Cicer

(c) Pisum

(d) Alnus

Answer/Explanation

Ans. (a)

 

Question

 Maximum nutritional diversity is found in the group [CBSE AIPMT 2010]

(a) Fungi

(b) Animalia

(c) Monera

(d) Plantae

Answer/Explanation] 

Ans. (c)

Maximum nutritional diversity is shown by the members of kingdom-Monera.

Question

 Some hyperthermophilic organisms that grow in highly acidic habitats belong to the two groups called [CBSE AIPMT 2010]

(a) eubacteria and archaea

(b) cyanobacteria and diatoms

(c) protists and mosses

(d) liverworts and yeasts

Answer/Explanation

Ans. (a)
Thermophiles live in very hot places, with temperature ranging from $60^{\circ}-80^{\circ} \mathrm{C}$. Many thermophiles (some eubacteria and archaebacteria) are autotrophs and have metabolisms based on sulphur.

Question

 Thermococcus, Methanococcus and Methanobacterium exemplify [CBSE AIPMT 2008]

(a) archaebacteria that contain protein homologous to eukaryotic core histones

(b) archaebacteria that lack any histones resembling those found in eukaryotes but whose DNA is negatively supercoiled

(c) bacteria whose DNA is relaxed or positively supercoiled but which have a cytoskeleton as well as mitochondria

(d) bacteria that contain a cytoskeleton and ribosomes

Answer/Explanation

Ans. (a)

Inspection of domain Archaea shows that two sub-divisions exist, the Euryarchaeota and the Crenarchaeota.

Question

 Bacterial leaf blight of rice is caused by a species of [CBSE AIPMT 2008]

(a) Xanthomonas

(b) Pseudomonas

(c) Alternaria

(d) Erwinia

Answer/Explanation

Ans. (a)
Disease Causing Organism Leaf blight of rice -Xanthomonas oryzae
Redstrip of suga – Pseudomonos cane rubrilineans
Fire blight of apple – Erwinia amylovora

Question

 Which one of the following statements about Mycoplasma is wrong? [CBSE AIPMT 2007]

(a) They are also called PPLO

(b) They are pleomorphic

(c) They are sensitive to penicillin

(d) They cause disease in plants

Answer/Explanation

Ans. (c)

 

Question

 Barophillic prokaryotes [CBSE AIPMT 2005]

(a) grow slowly in highly alkaline frozen takes at high altitudes

(b) occur in water containing high concentrations of barium hydroxide

(c) grow and multiply in very deep marine sediments

(d) readily grown and divides in sea water enriched in any soluble salt of barium

Answer/Explanation

Ans. (c)

 

Question

 A free living nitrogen fixing cyanobacterium which can also form symbiotic association with the water fern Azolla is [CBSE AIPMT 2004]

(a) Tolypothrix

(b) Chlorella

(c) Nostoc

(d) Anabaena

Answer/Explanation

Ans. (d)

 

Question

 Chromosomes in a bacterial cell can be 1-3 in number and [CBSE AIPMT 2003]

(a) can be circular as well as linear within the same cell

(b) are always circular

(c) are always linear

(d) can be either circular or linear, but never both within the same cell

Answer/Explanation

Ans. (b)

 

Question

 Organisms which obtain energy by the oxidation of reduced inorganic compounds are called [CBSE AIPMT 2002]

(a) homoautotrophs

(b) chemoautotrophs

(c) saprozoic

(d) coproheterotrophs

Answer/Explanation

Ans. (b)

The organisms obtaining energy by chemical reactions independent of light are called chemotrophs. The reductants obtained from the environment may be inorganic (in case of chemoautotrophs) or organic (in case of chemoheterotrophs).
Photoautotrophs organisms that make their own food by photosynthesis, using the light energy.

Question

 In bacteria, plasmid is [CBSE AIPMT 2002]

(a) extra-chromosomal material

(b) main DNA

(c) non-functional DNA

(d) repetitive gene

Answer/Explanation

Ans. (a)

 

Question

 What is true for archaebacteria?

(a) All halophiles

(b) All photosynthetic

(c) All fossils

(d) Oldest living beings

Answer/Explanation

Ans. (d)

Question

What is true for cyanobacteria? [CBSE AIPMT 2001]

(a) Oxygenic with nitrogenase

(b) Oxygenic without nitrogenase

(c) Non-oxygenic with nitrognase

(d) Non-oxygenic without nitrogenase

Answer/Explanation

Ans. (a)

Cyanobacteria (Gk. Kyanos = dark blue; bakterion = a staff)also known as blue-green algae. It is a very important group of photosynthetic bacteria in the history of life on earth.

Question

 What is true for photolithotrophs? [CBSE AIPMT 2001]

(a) Obtain energy from radiations and hydrogen from organic compounds

(b) Obtain energy from radiations and hydrogen from inorganic compounds

(c) Obtain energy from organic compounds

(d) Obtain energy from inorganic compounds

Answer/Explanation

Ans. (b)

 

Question

Photosynthetic bacteria have pigments in [CBSE AIPMT 1999]

(a) leucoplasts

(b) chloroplasts

(c)chromoplasts

(d) chromatophores

Answer/Explanation

Ans. (d)

In photosynthetic bacteria, small particles of $60 \mu$ mdiameter, called chromatophores, are present. These are attached to the inner surface of the cell membrane, have no limiting membrane and possess bacteriochlorophyll.
Chloroplast, leucoplast and chromoplasts are plastids present in eukaryotic cells.
(a) Chromoplasts Coloured plastids except green, give different type of colour appearance to different parts of the plant.
(b) Chloroplasts Green plastids take part in the process of photosynthesis.
(c) Leucoplasts

Question

A few organisms are known to grow and multiply at temperatures of $100-105^{\circ} \mathrm{C}$. They belong to [CBSE AIPMT 1998]
(a) marine archaebacteria
(b) thermophilic sulphur bacteria
(c) hot-spring blue-green algae (cyanobacteria)
(d) thermophilic, subaerial fungi

Answer/Explanation

Ans. (a)

Question

 The hereditary material present in the bacterium Escherichia coli is [CBSE AIPMT 1997, 98]

(a) single stranded DNA

(b) deoxyribose sugar

(c) double stranded DNA

(d) single stranded RNA

Answer/Explanation

Ans. (c)

Question

 Bacterium divides every 35 minutes. If a culture containing $10^5$ cells per $\mathrm{mL}$ is grown for 175 minutes, what will be the cell concentration per $\mathrm{mL}$ after 175 minutes? [CBSE AIPMT 1998]

(a) $5 \times 10^5$ cells

(b) $35 \times 10^5$ cells

(c) $32 \times 10^5$ cells

(d) $175 \times 10^5$ cells

Answer/Explanation

Ans. (c)
$
\begin{aligned}
& 1 \times 10^5 \stackrel{35 \mathrm{~min}}{\longrightarrow} 2 \times 10^5 \stackrel{70 \mathrm{~min}}{\longrightarrow} 4 \times 10^5 \\
& \stackrel{105 \mathrm{~min}}{\longrightarrow} 8 \times 10^5 \stackrel{140 \mathrm{~min}}{\longrightarrow} 16 \times 10^5 \\
& \stackrel{175 \mathrm{~min}}{\longrightarrow} 32 \times 10^5
\end{aligned}

Question

 The site of respiration in bacteria is [CBSE AIPMT 1997]

(a) episome

(b) mesosome

(c) ribosome

(d) microsome

Answer/Explanation

Ans. (b)

The cytoplasmic membrane of bacteria is invaginated at certain places into the cytoplasm in the form of tubules, which are called mesosomes; on their surface are found enzymes associated with respiration.

 

Question

 In bacterial chromosomes, the nucleic acid polymers are [CBSE AIPMT 1996]

(a) linear DNA molecule

(b) circular DNA molecule

(c) of two types – DNA and RNA

(d) linear RNA molecule

Answer/Explanation

Ans. (b)

 

Question

Sex factor in bacteria is [CBSE AIPMT 1996]

(a) chromosomal replicon

(b) F-replicon

(c) RNA

(d) sex-pilus

Answer/Explanation

Ans. (b)

Question

The plasmid [CBSE AIPMT 1995]

(a) helps in respiration

(b) genes found inside nucleus

(c) is a component of cell wall of bacteria

(d) is the genetic part in addition to DNA in microorganisms

Answer/Explanation

Ans. (d)

 

Question

Temperature tolerance of thermal blue-green algae is due to [CBSE AIPMT 1994]

(a) cell wall structure

(b) cell organisation

(c) mitochondrial structure

(d) homopolar bonds in their proteins

Answer/Explanation

Ans. (a)

 

Question

 Escherichia coli is used extensively in biological research as it is [CBSE AIPMT 1993]

(a) easily cultured

(b)easily available

(c) easy to handle

(d) easily multiplied in host

Answer/Explanation

Ans. (a)

Question

 Genophore bacterial genome or nucleoid is made of [CBSE AIPMT 1993]

(a) histones and non-histones

(b) RNA and histones

(c) a single double stranded DNA

(d) a single stranded DNA

Answer/Explanation

Ans. (c)

In bacteria nucleoid or genophore is haploid and consists of single, naked, double stranded, circular ring like highly folded supercoiled DNA with no free ends, no histone proteins.

Question

 Bacteria lack alternation of generation because there is [CBSE AIPMT 1992, 91]

(a) neither syngamy nor reduction division

(b) distinct chromosomes are absent

(c) no conjugation

(d) no exchange of genetic material

Answer/Explanation

Ans. (a)
Bacteria reproduces asexually by transverse binary fission, conidia, budding, cyst and sporulation. No true sexual reproduction (involving formation of gametes, their fusion and meiosis) is known to occur in bacteria.
However, in bacteria the transfer of genetic material from donor to recipient cell to bring genetic

Question

Which one belongs to the Monera? [CBSE AIPMT 1990]

(a) Amoeba

(b) Escherichia

(c) Gelidium

(d) Spirogyra

Answer/Explanation

Ans. (b)

The kingdom-Monera (Gr. monera = simple) includes simple, prokaryotic primitive organisms. It includes bacteria, archaebacteria, Actinomycetes;
Mycoplosma, spirochaetes, rickettsiae, chlamydiae and cyanobacteria.

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